This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. When administered by oral inhalation using a dry powder inhaler DAS181 is intended to treat naturally acquired influenza. . This is a randomized, double-blinded, dose escalating Phase 1 study of a single dose treatment with DAS181 in healthy adults. Subjects will be randomized in a 2:1 ratio to receive either a single dose treatment with DAS181 or placebo. The study is designed to explore the safety and tolerability of a single dose treatment with DAS181, based on a combination of the adverse event rates, immunogenicity profile and pharmacokinetic profile. The data from this study will be used to select the dose levels for future studies. The study will be conducted in dose escalating steps, which will start from the lowest dose level and move to the higher dose levels after dose escalating criteria are met. Within each dose group, study drug dosing will be initiated in staggered steps. The subjects will be followed for 30 days after dosing.